On Tue, Jan 22, 2019 at 07:59:32AM -0800, Ram Pai wrote: > plpar_ucall() function can now be used to make ucalls > with varied number of in and out arguments. It handles > 4 out arguments and a lot of in arguments. > > copies the implementation of plpar_hcall(). > > Signed-off-by: Ram Pai <linuxram@xxxxxxxxxx> > --- > arch/powerpc/platforms/powernv/Makefile | 1 + > arch/powerpc/platforms/powernv/uvCall.S | 41 +++++++++++++++++++++++++++++++++ I don't think arch/powerpc/platforms/powernv is the right place for this, since we will also need to do ucalls from a secure guest and its kernel may not have CONFIG_PPC_POWERNV=y. Also, the "plpar_" prefix gives rise to a cognitive dissonance, because "plpar" is short for pSeries logical partition, and we definitely are not in a pSeries logical partition here. > +_GLOBAL_TOC(plpar_ucall) > + > + mfcr r0 > + stw r0,8(r1) > + mr r0,r3 > + > + std r4,STK_PARAM(R4)(r1) /* Save ret buffer */ > + > + mr r3,r5 > + mr r4,r6 > + mr r5,r7 > + mr r6,r8 > + mr r7,r9 > + mr r8,r10 > + > + sc 2 /* invoke the ultravisor */ > + > + ld r12,STK_PARAM(R4)(r1) > + std r4, 0(r12) > + std r5, 8(r12) > + std r6, 16(r12) > + std r7, 24(r12) > + > + lwz r0,8(r1) > + mtcrf 0xff,r0 > + > + blr /* return r3 = status */ So we save/restore CR across the ucall, but not LR. Do we really not trust the ultravisor to preserve the non-volatile CR fields, or is it just that you were copying plpar_hcall()? Either way it deserves a note in the patch description. Paul.
